1. Field of the Invention
The present invention relates generally to manhole lining techniques, and more particularly to a liner bag for use in lining of a manhole, which has a two-layer structure composed of an inner-layer liner bag and an outer-layer liner bag, and a method of lining a manhole using this two-layer liner bag.
2. Description of the Related Background Art
When a manhole having a reducer section toward an opening becomes defective or too old to perform properly, the manhole is repaired and rehabilitated by lining the inner wall thereof without digging the earth to expose the manhole and disassembling the sections of the manhole. This non-digging method of repairing a manhole has been known and practiced commonly in the field of civil engineering.
A liner bag for use in lining of a manhole is typically designed to have a relatively large thickness so as to endure water pressure and earth pressure for a long term.
It is however extremely difficult to shape a thick resin absorbent material into a complicated bag form conformal to the shape of an existing manhole including a reducer and so on. On top of that, it is almost impossible to air-tight coat a plastic film, serving as a fluid pressure barrier film, on the surface of such a resin absorbent material in the form of a bag.
To overcome the difficulties inherent to the lining of a manhole, there has been proposed a method of lining a manhole using a fluid pressure barrier liner which is separate from a liner bag. This manhole lining method will be described below with reference to FIGS. 8 to 10.
FIGS. 8 to 10 are cross-sectional views illustrating a conventional manhole lining method in order. Specifically, in this manhole lining method, a manhole lining bag 101 is inserted into an existing manhole 106 from the ground, and an opening at the upper end of the lining bag 101 is fitted on a lower portion of a fixing collar 107 installed on the ground, as can be seen in FIG. 8. The liner bag 101 is formed of a tubular resin absorbent material which has a portion formed to match the shape of a reducer section 106a of the existing manhole 106 (tapered form), and an unhardened thermosetting resin impregnated in the resin absorbent material.
In addition, a fluid pressure barrier liner 130 formed of a highly air-tight plastic tube is folded out such that one end thereof is also fitted on the lower portion of the fixing collar 107. When the insertion of the liner bag 101 into the manhole 106 is completed, water is poured into the inside of the folded-out fluid pressure barrier liner 130 from a water supply hose 115. The poured water causes the fluid pressure barrier liner 130, receiving the pressure (weight) of the water, to evert and go downward into the lining bag 101.
Then, after the fluid pressure barrier liner 130 has been completely everted and inserted into the liner bag 101, a hot water hose 118 attached to an extreme end of the fluid pressure barrier liner 130 is drawn into the fluid pressure barrier liner 130, as illustrated in FIG. 9. The cross-sectional view of FIG. 9 includes, as tools associated with the lining of the manhole 106, a pipeline 108 running below the manhole 106; a water passing hose 109 for passing water within the pipe line 108 during the lining of the manhole; a filler 110; and water stopping plugs 127, 128.
Next, as illustrated in FIG. 9, a cap 116 is placed on the upper opening of the fixing collar 107 and secured to the same to form a sealed space S within the fluid pressure barrier liner 130.
The hot water hose 118 and a drain hose 119 have been drawn into the sealed space S. A portion of the drain hose 119 extending out of the sealed space S has an end open to the top of a hot water tank 120 installed on the ground.
A water supply pipe 121 extending from a lower portion of the hot water tank 120 is connected to an inlet of a boiler 122, and a hot water pump 123 is interposed on the middle of the water supply pipe 121. One end of the hot water hose 118 is connected to the outlet side of the boiler 122. In addition, an air hose 125 extending out from a compressor 124 is connected to the cap 116.
When the compressor 124 is driven to supply compressed air into the sealed space S through the air hose 125, the fluid pressure barrier liner 130 and the liner bag 101 are pressed onto the inner wall of the manhole 106 by the pressure of the compressed air.
Next, with the foregoing condition being maintained, the boiler 122 and the hot water pump 123 are driven to supply the hot water within the hot water tank 120 to the boiler 122. After heated to a predetermined temperature by the boiler 122, the hot water is supplied into the sealed space S through the hot water hose 118. Specifically, the hot water running through the hot water hose 118 is sprayed out into the sealed space S just like shower from a plurality of spray holes formed through a portion of the hot water hose 118 that faces the sealed space S.
The hot water, which has served to heat the liner bag 101 and cooled down, drops and accumulates in the bottom of the sealed space S. This hot water accumulating in the bottom is urged by an inner pressure of the sealed space S to go back to the hot water tank 120 through the drain hose 119. Then, it is again supplied to the boiler 122 by the hot water pump 123, and heated by the boiler 122. Subsequently, the foregoing operations are repeated.
When the hot water is cyclically sprayed out from the hot water hose 118 through the circuit formed of the hot water hose 118, the drain hose 119, the hot water tank 120, the water supply pipe 121, the hot water pump 123 and the boiler 122, the lining bag 101 is heated to cause the thermosetting hardenable resin impregnated therein to be uniformly hardened. After the thermosetting resin impregnated in the lining bag 101 has been hardened, the fluid pressure barrier liner 130 is stripped off to remove the same from the lining bag 101, as illustrated in FIG. 10. As a result, the inner wall of the manhole 106 has been lined or repaired by the hardened liner bag 101, followed by the completion of a sequence of the lining works after unnecessary portions of the hardened liner bag 101 are cut.
The conventional manhole lining method described above, however, implies problems related to the durability of the hardened liner bag and the working cost. Specifically, since the fluid pressure barrier liner 130 is stripped off and disposed as waste after the completion of the lining, the durability of the liner bag cannot be increased by covering the surface of the hardened liner bag 101, after lined on the inner wall of the manhole, with a barrier film. In addition, an effort of stripping off the fluid pressure barrier liner 130 is additionally required, with an additional cost for disposing the stripped fluid pressure barrier liner 130 as a waste.
The present invention has been made in view of the problems mentioned above, and it is an object of the present invention to provide a liner bag for a manhole which can have an improved durability after hardening with a fluid pressure barrier film being left on the inner wall of a manhole to be lined, and a method of lining a manhole using the liner bag which is capable of realizing a reduction in the number of steps involved in a manhole lining process to reduce a working time and a working cost.
To achieve the above object, in a first aspect of the present invention, there is provided a liner bag for a manhole which comprises an outer-layer liner bag including a first bag-shaped resin absorbent material, and an unhardened liquid hardenable resin impregnated in the first bag-shaped resin absorbent material, and an inner-layer liner bag including a second bag-shaped resin absorbent material, a highly air-tight plastic film coated over an inner surface of the second bag-shaped resin absorbent material, and an unhardened liquid hardenable resin impregnated in the second bag-shaped resin absorbent material, wherein the inner-layer liner bag has a thickness smaller than the outer-layer liner bag, and the inner-layer liner bag being inserted in the outer-layer liner bag.
Preferably, the outer-layer liner bag has an outer diameter smaller than an inner diameter of an existing manhole by 2% to 20% to form a clearance between the outer-layer liner bag and the existing manhole, and the inner-layer liner bag has an inner diameter smaller than the inner-diameter of the outer-layer liner bag by 2% to 20% to form a clearance between the inner-layer and outer-layer liner bags. The outer-layer liner bag and the inner-layer liner bag may respectively have a reducer portion, and the length of the outer-layer liner bag except for the reducer portion is set shorter than the depth of the existing manhole except for a reducer section of the existing manhole, wherein the length of the outer-layer liner bag except for the reducer portion is set shorter than the length of the outer-layer liner bag except for the reducer portion. The thickness of the second resin absorbent material constituting the inner-layer liner bag may be set to a range of 2 m/m to 12 m/m when it is applied with a load of 200 g/cm2. The second resin absorbent material of the inner-layer liner bag may be made of unwoven fabric, and the plastic film coated over the inner surface of the resin absorbent material is formed of a polyurethane film having a Shore hardness equal to or larger than 85 and a thickness equal to or larger than 0.25 m/m. The second resin absorbent material constituting the inner-layer liner bag may be made of unwoven fabric having a weight ranging from 100 g/m2 to 1500 g/m2.
The highly air-tight plastic film coated over the inner surface of the second bag-shaped resin absorbent material is left as a fluid pressure barrier film after the manhole liner bag has been hardened.
According to a second aspect of the present invention, there is provided a method of lining a manhole comprising the steps of providing an outer-layer liner bag including a first bag-shaped resin absorbent material, and an unhardened liquid hardenable resin impregnated in the first bag-shaped resin absorbent material, providing an inner-layer liner bag including a second bag-shaped resin absorbent material, a highly air-tight plastic film coated over an inner surface of the second bag-shaped resin absorbent material, and an unhardened liquid hardenable resin impregnated in the second bag-shaped resin absorbent material, the inner-layer liner bag having a thickness smaller than the outer-layer liner bag, inserting the outer-layer liner bag into an existing manhole, everting and inserting the inner-layer liner bag into the outer-layer liner bag to form a manhole liner bag, acting a fluid pressure on a sealed space formed within the manhole liner bag to press the manhole liner bag onto an inner wall of the existing manhole, and hardening the liquid hardenable resin impregnated in the first resin absorbent material of the outer-layer liner bag and the second resin absorbent material of the inner-layer liner bag.
The highly air-tight plastic film coated over the inner surface of the second bag-shaped resin absorbent material is not stripped off but is left as a fluid pressure barrier film after the manhole liner bag has been hardened.
As appreciated, according to the method of lining a manhole using the manhole liner bag of the present invention, since the manhole lining method eliminates the necessity of stripping off the highly air-tight plastic film from the hardened liner bag and wasting the same, as before, it is possible to realize a reduction in the number of steps involved in the lining process, a working term, and a working cost.
Furthermore, the plastic film, functioning as a fluid pressure barrier film during the lining process, remains as it is on the inner surface of the hardened liner bag, after the lining, so that the surface of the liner bag, as a hardened material, is covered with and protected by the plastic film to increase the durability of the liner bag.
The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments thereof when read in conjunction with the accompanying drawings.